Na-ion conductivity of β-NaFeO2 synthesized from an EDTA chelate complex

Abstract In this study, Na-ion conductivity of β-NaFeO2 was improved by a low-temperature synthesis. A precursor Fe-complex containing ethylenediamine tetraacetate (EDTA) was prepared and then calcined at temperatures of 500–800 °C under flowing air (on heating) and Ar gas (on cooling). Single-phase β-NaFeO2 powder was obtained at temperatures of 600–750 °C. The specific surface area of the β-NaFeO2 powder increased as the calcination temperature decreased. The β-NaFeO2 compact fabricated from the powder calcined at 600 °C had the largest density. Alternating current impedance analysis revealed that the resistivity of the grain boundaries in the compact decreased with increasing density, which improved the Na-ion conductivity of β-NaFeO2. Thus, the Na-ion conductivity of β-NaFeO2 was successfully improved by increasing its specific surface area.